Water is commonly stored above ground or underground in an appropriate containment structure or the like as a reserve for use during times of peak water usage. A water treatment plant may be fluidly interconnected with the containment structure to treat the water prior to storage and/or to treat the water after been retrieved from storage for subsequent use. In any case, water may be withdrawn from this containment structure and thereafter used for any appropriate purpose. Typically these types of containment structures are vented above ground. As such, it may be possible to introduce a hazardous substance into the containment structure through the above-ground vent, which of course would be undesirable.